Can Anastrozole Cause Erectile Dysfunction?

What is anastrozole?

Anastrozole is a type of medication called an aromatase inhibitor (AI).

Aromatase is an enzyme your body uses to convert testosterone into estrogen. 

Anastrozole works by blocking the action of aromatase, slowing down the conversion process, and resulting in higher testosterone and lower estrogen levels in the body.

Uses

Anastrozole¹ is FDA-approved to treat certain types of breast cancers. Some cancers require hormones like estrogen to grow. Anastrozole can help by decreasing the levels of estrogen in the body. 

Anastrozole may also be prescribed off-label to treat other conditions. One is male hypogonadism, a condition where the testicles do not produce enough testosterone. It may also be prescribed for men undergoing testosterone replacement therapy (TRT).

If a medication is prescribed off-label, your healthcare provider prescribes it for a purpose different from the FDA approved. 

The particular purpose for which the medication has been prescribed is not included on its label, and the FDA does not guide the drug's usage. Your healthcare provider may prescribe a medication off-label at their discretion. 

The link between anastrozole and erectile dysfunction

Estrogen is often thought of as a female hormone, and testosterone is a male hormone. However, everyone has a combination of both hormones in their bodies. Both males and females require balanced hormone levels for their bodies to function well.

For men, too little testosterone or too much estrogen in their bodies can lead to issues with sexual functioning, such as low libido, low sperm production, fatigue, and erectile dysfunction. 

AI medications, like anastrozole, may be used to help restore hormones to balance levels.

Studies on anastrozole in men have not produced evidence that it directly causes erectile dysfunction. 

However, healthy estrogen levels are essential for male sexual functioning, and estrogen levels that are too low may contribute to erectile dysfunction. As such, estrogen levels mustn't drop too low during hormone treatments. 

How does anastrozole cause erectile dysfunction?

You've likely heard that optimal testosterone levels are crucial for healthy sexual functions, such as achieving an erection. 

Though this is the case, estrogen can also influence sexual functioning. Men may have issues with sexual functioning if estrogen levels do not stay within a healthy range or if there is an imbalance in the ratio of testosterone to estrogen.

Estrogen levels that are too high may lead to an increased incidence of ED, while estrogen levels that are too low may lead to decreased libido. 

As mentioned earlier, research has not shown that anastrozole causes erectile dysfunction. However, as maintaining healthy testosterone to estrogen ratios is important for maintaining sexual desire, some research² suggests a cautious approach to using AI medications under certain circumstances, such as when used with testosterone hormone treatments.

Additionally, they suggest monitoring estrogen and testosterone hormone levels during hormone treatments may be necessary. 

Why would a man take anastrozole?

As men age, their testosterone levels may decrease. Low testosterone levels can cause decreased bone mineral density, decreased body mass, fatigue, and issues with sexual function, such as erectile dysfunction. 

Some men may have certain conditions that cause hormonal imbalances, and overweight men often have low testosterone levels and associated issues. 

Testosterone replacement therapy (TRT) is often used to help increase testosterone levels in men and restore healthy body functions. Sometimes though, an increase in testosterone may also lead to a rise in estrogen. 

This estrogen increase may occur because higher testosterone levels give the body more material to convert into estrogen, potentially causing estrogen levels to become too high. Men may be prescribed anastrozole with TRT to manage this issue.

Men may be prescribed anastrozole increase testosterone levels on its own as an alternative to TRT. Some healthcare providers may recommend this option, particularly if a man wishes to have children.

Although beneficial for increasing testosterone levels, TRT can lead to subfertility. As anastrozole slows the body from converting testosterone to estrogen, it may help increase testosterone levels.

However, a review found that anastrozole doesn’t improve sex drive, erections, or semen quality — so their usefulness is limited. 

Benefits of anastrozole in men

Increasing testosterone levels can help alleviate the issues associated with low testosterone, such as erectile dysfunction. As mentioned earlier, anastrozole may be prescribed to help increase testosterone levels in men. 

There is currently limited evidence of anastrozole's effectiveness in treating erectile dysfunction. A 2004 study³ found that anastrozole increased testosterone levels to healthy ranges in older men with low testosterone levels. Additionally, estrogen levels decreased but remained in healthy ranges during treatment.

A more recent 2017 study⁴ found that anastrozole increased testosterone levels and sperm quality in men with low testosterone.

However, a 2019 analysis⁵ of anastrozole showed that although it increased testosterone levels in participants, it didn't directly treat erectile dysfunction.

TRT is effective for increasing testosterone levels. But, because it may also increase estrogen levels, it could cause sexual functioning issues and the growth of male breast tissue. 

Taking anastrozole in combination with TRT may help prevent these issues. Additionally, if a man wishes to prevent fertility issues, anastrozole may be an alternative treatment option that can increase testosterone levels. 

Side effects of anastrozole in men

A recent review⁶ of alternative treatments to TRT showed that AI medications, such as anastrozole, were mostly well-tolerated by men using them to increase testosterone levels. However, some reported side effects include:

• Nausea

• Increased liver enzymes

• Headaches

• Hot flashes

Some studies recommended against using AI medications, like anastrozole, as men have an association between long-term use and decreased bone mineral density. Decreased bone density causes bones to become weak, leading to an increased risk of fractures.

Some research⁶ states that AI medications should not be used for prolonged periods due to potential decreases in bone density. 

Although anastrozole is effective at increasing testosterone levels, further studies are needed to determine if it is effective for treating erectile dysfunction. 

The lowdown

Testosterone and estrogen levels that are too high or too low can lead to issues with sexual functioning, such as erectile dysfunction. Anastrozole may be prescribed off-label to address these hormonal imbalances. 

Because anastrozole inhibits the body from producing estrogen, it could lead to erectile dysfunction, but research has not shown this effect. Anastrozole is effective at increasing testosterone levels and possibly safe in certain dosages. 

However, research has not yet shown anastrozole to be effective for directly treating erectile dysfunction, and more research is needed to determine if it is effective for this purpose.